CN101159518B - Communication method and communication device - Google Patents

Communication method and communication device Download PDF

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Publication number
CN101159518B
CN101159518B CN2007101471651A CN200710147165A CN101159518B CN 101159518 B CN101159518 B CN 101159518B CN 2007101471651 A CN2007101471651 A CN 2007101471651A CN 200710147165 A CN200710147165 A CN 200710147165A CN 101159518 B CN101159518 B CN 101159518B
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grouping
groups
packet
ack
communication
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CN101159518A (en
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迫田和之
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Sony Corp
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Sony Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access, e.g. scheduled or random access
    • H04W74/08—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access]
    • H04W74/0808—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access] using carrier sensing, e.g. as in CSMA
    • H04W74/0816—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access] using carrier sensing, e.g. as in CSMA carrier sensing with collision avoidance
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0002—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
    • H04L1/0025—Transmission of mode-switching indication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0072—Error control for data other than payload data, e.g. control data
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/1607—Details of the supervisory signal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H04L12/407—Bus networks with decentralised control
    • H04L12/413—Bus networks with decentralised control with random access, e.g. carrier-sense multiple-access with collision detection (CSMA-CD)
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
    • H04L69/22—Parsing or analysis of headers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/18—Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

In a communication within a network consisting of a plurality of communication stations, access control is performed so that a packet communication timing will no collide with another station by detecting a signal transmitted from that station. ''A header area processed to be not liable to err like a packet physical layer header portion'' transmitted from the communication station contains at least information necessary for information extraction of the packet payload and a field for controlling access reservation of a packet transmission caused by a packet transmission, so that a processing using the field can be performed.

Description

Communication means and communication equipment
The application is to be that February 3, application number in 2004 are 200480000082.4, are entitled as the dividing an application of application of " communication means and communication equipment and computer program " applying date.
Technical field
The present invention relates to a kind of WLAN that is fit to be applied to for example to carry out data communication etc. (local area network (LAN): the local message communication network) communication means of system and communication equipment and computer program, particularly use CSMA (carrier wave detection multiple access) to carry out the technology under the situation of visit.
Background technology
Traditionally, as the medium access control in the Wireless LAN system, are well-known by the access control of regulations such as IEEE (IEEE) 802.11 methods.The detailed description of IEEE802.11 method is seen international standard ISO/IEC8802-11:1999 (E) ANSI/IEEE standard 802.11,1999 editions, part 11: WLAN medium access control (MAC) and physical layer (PHY) standard etc.
Use Figure 12 that the accessing competition method according to conventional I EEE802.11 method is described.In the IEEE802.11 method, four kinds of IFS (interframe space) have been defined as the class interval.Wherein three kinds are described here.As IFS, SIFS (short IFS), PIFS (PCF IFS) and DIFS (DCFIFS) are according to defining from being short to long length order.In IEEE802.11; Adopt CSMA (carrier wave detection multiple access) as basic medium access process; Wherein, before transmitter sends something, keep out of the way (back-off) timer and on a random time section, work; The state of monitoring media simultaneously, and have only and when in this time period, not having the transmission signal, just give transmission route.
When (being called DCF: when distributed coordination function) sending normal packets according to the CSMA process; The state of the DIFS monitoring media in the time period after the transmission of accomplishing certain grouping at first; If in this time period, there is not the transmission signal; Then carry out random back, and if in this time period, also do not exist and send signal then give transmission route.On the other hand, the grouping that has a high urgency when transmission is as when confirming the ACK of response signal, and allowing the SIFS class interval after, to send should grouping.Therefore, might earlier send grouping according to the normal packets of CSMA process transmission by beguine with high urgency.
Why Here it is defines the reason of dissimilar IFS, and for the conflict of grouping transmission route, is SIFS, PIFS or DIFS according to IFS, confirms priority order.
Next step is an example with the IEEE802.11a as the extension standards of IEEE802.11, and uses Figure 13 and 14 that frame format (packet format) is described.Figure 13 is the figure that illustrates according to the frame format of IEEE802.11a.The stem that preposition (preamble) is added to each grouping exists with what expression was divided into groups.According to this standard, the known symbol pattern is defined as preposition, and receiver judges that according to this known mode whether qualified receive signal is preposition.
After preposition, defined signal field.Message part to dividing into groups is decoded required information stores in signal field.The required information of decoding to dividing into groups is called PLCP header (Physical Layer Convergence Protocol header); And the speed field that the PLCP header comprises the transmission rate of representing message part (in addition; Also comprise service fields as the part of PLCP header; But, below for the purpose of simplifying the description for the purpose of and its general designation is made message part), data length field, the Parity Check Bits of the length of expression message part, the tail of encoder compare top grade.Receiver is carried out the decode operation of message part subsequently according to the speed of PLCP header and the decoded result of length field.
Antimierophonic coding is applied to storing the signal section of PLCP header, and carries out transmission with the speed that equals 6Mbps.On the other hand, the message part in the ordinary groups sends with the transmission rate pattern that bit rate is provided in the scope according to the least possible mistake of generations such as SNR in receiver.Shown in figure 13, in IEEE802.11a, defined altogether eight kinds of transmission rate patterns promptly 6,9,12,18,24,36,48 and 54Mbps.
Therefore, under near the situation of sending being in receiving equipment, selection has the transmission rate pattern of bit rate, and in the communication station that is arranged in the distant place this information to be decoded possibly be impossible.Message part is sent to the link layer as the upper strata as PSDU (physical layer Service Data Unit).
Figure 14 is the figure that the frame field of PSDU is shown.Though in IEEE802.11, defined some frame types, only explained here for three kinds of necessary frames of explanation.
Frame control field and duration field jointly are defined in each frame.The information stores of the kind of expression frame, use etc. is in frame control field.And the information stores that is used for NAV (network allocation vector) that the back specifies is in the duration field, and writes the time period till accomplishing packet transactions therein.In Frame, be different from above-mentioned, exist four address fields being used for specifying transmission source, purpose communication station etc., sequence field (SEQ), as the frame main body of the clean information that will offer the upper strata and as verification and FCS (Frame Check Sequence).In the RTS frame, be different from above-mentioned, exist the expression destination receiver address (RA), expression transmission source transmitter address (TA) and as verification and FCS.In CTS frame and ACK frame, be different from above-mentioned, exist the expression destination RA and as verification and FCS.
Use Figure 11 and 15 that the RTS/CTS process among the IEEE802.11 is described.In the wireless lan network of special (ad hoc) environment, generally well-knownly be the problem of concealed terminal to take place and be known as the method that is used to solve most of this problem according to the CSMA/CA of RTS/CTS process.This method also is used for IEEE802.11.
Use Figure 11 that the example of the operation in the RTS/CTS process is described.Figure 11 illustrates the example that certain information (data) is sent to the STA1 of communication station from the STA0 of communication station.Before sending actual information, the STA0 of communication station sends RTS (request is sent) according to the CSMA process to the STA1 of communication station as the information destination and divides into groups.When the STA1 of communication station receives this grouping, be used for feeding back the CTS (clear to send) that receives RTS to the STA0 of communication station transmission and divide into groups.When the reception of CTS is carried out on the ground of fault-free in the STA0 of communication station, think that then medium is without hindrance and sends information (data) immediately and divide into groups.After fault-free ground is accomplished and received in the STA1 of communication station, return transmission and the reception affairs of ACK to accomplish a grouping.
Use Figure 15 that the operation that in this process, takes place is described.In Figure 15, the example that has the STA2 of communication station, STA0, STA1 and STA3 and have only communication station adjacent one another are just to be in the reception and registration scope of electric wave is described.In addition, be assumed to the situation that the STA0 of communication station sends the information that is addressed to the STA1 of communication station.Confirm according to above-mentioned CSMA process medium at the fixed time in the section (from time T 0 to time T1) without hindrance after, the STA0 of communication station begins to send the RTS that is addressed to the STA2 of communication station in time T 1 and divides into groups.The expression grouping is that the information of RTS is written in the frame control field of RTS grouping; Time period till the transmission of accomplishing that grouping and reception affairs (just; Time period till time T 8) is written in the duration field; The address of purpose communication station (STA1) is written in the RA field, and its address (STA0) is written in the TA field.
Here; It should be noted that more like this; Be the STA0 of communication station need confirm to accomplish affairs when sending RTS time, therefore be necessary to make the transmission rate pattern of CTS grouping, packet and the ACK grouping of sending subsequently and receiving when sending RTS, to become definite.
This RTS divides into groups also to be received by near the STA2 of communication station the STA0 of communication station.When receiving the RTS signal, the STA2 of communication station begins to receive operation when discovery is preposition, and according to through the information that obtains that the PLCP header is decoded PSDU being decoded.Frame control field from PSDU identifies and divides into groups to be that RTS divides into groups and to know that the STA0 of communication station will send certain information.And identifying the STA2 of communication station from the RA field is not the purpose communication station.Then; For the transmission of not interrupt communication station STA0, the STA2 of communication station knows that medium is in seizure condition under the situation of monitoring media not, and stops to send till accomplishing these affairs; Just, in example shown in Figure 15 till accomplishing the time T 8 that ACK sends.This operation is called NAV (network allocation vector) etc. is set.In being provided with the state of NAV, NAV is effective on the represented time period in the duration field, and the STA2 of communication station is in the transmission illegal state till time T 8.
On the other hand, this RTS divides into groups also to be received by the STA1 of communication station as its destination.When through PSDU is decoded, when the STA1 of communication station identified the STA0 of communication station and will send the grouping that is addressed to it with the mode that is similar to said process, STA1 returned the CTS grouping in the time T 3 of SIFS after at interval.The transmission rate pattern that CTS divides into groups should be same as the transmission rate pattern of RTS.And; Grouping is that CTS divides into groups to be written in the frame control field of PSDU; Time period (just, the time period till time T 8) till accomplishing affairs is written in the duration field, and the address of purpose communication station (STA1) is written in the RA field.
This CTS divides into groups also to be received by near the STA3 of communication station the STA1 of communication station.The STA3 of communication station is similar near above-mentioned process PSDU is decoded identify " the communication station expection receives and divides into groups till time T 8 a certain " through use.Then, for the reception of not interrupt communication station STA1, the STA3 of communication station is provided with NAV to stop transmission, till accomplishing affairs.NAV is effective on the represented time period in the duration field, and the STA3 of communication station also is in the transmission illegal state till time T 8.
On the other hand, this CTS divides into groups also to be received by the STA0 of communication station as its destination.The STA0 of communication station is similar to above-mentioned process through use and PSDU is decoded identifies the STA1 of communication station and prepare to receive, and begins the transmission of packets in the time T 5 of SIFS after at interval.When the transmission of accomplishing packets in time T 6 and the STA1 of communication station decode to data error-free, return ACK in the time T 7 of SIFS after at interval, and the STA0 of communication station receives ACK to accomplish the transmission and the reception affairs of a grouping in time T 8.When time T8 arrives,, thereby turn back to normal transmission and accepting state as near the STA2 of communication station and STA3 removing (takedown) NAV of communication station.
In brief; Above-mentioned RTS divides into groups and CTS divides into groups through exchanging; In receiving " near the station as the STA0 of dispatching station " of RTS, forbid sending; And in receiving " near the station as the STA1 of receiving station " of CTS, forbid sending, thus do not receive near carry out under the unexpected transmission signal that sends of the station situation about disturbing by addressing and send for information and the returning of ACK from the STA0 of communication station to the STA1 of communication station.
Japan publication application No.H8-98255 discloses the conventional example of this access control of radio communication.
Simultaneously, in IEEE802.11, be necessary to make the transmission rate of RTS, CTS and packet when sending RTS, to be determined, thereby in the duration of RTS field, write the time period till accomplishing the transmission of dividing into groups and receiving affairs.Yet, following problem possibly appear according to this process.
-problem 1: the coverage area that (RTS divide into groups with) CTS divides into groups.
Though the transmission that CTS divides into groups under normal circumstances should be addressed to all communication stations of possible interrupt data branch group of received; But according to the IEEE802.11 standard; The CTS grouping need be sent with the transmission rate that is same as packet, and only between dispatching station and receiving station, carries out transmission with the transmission rate with minimum necessary noiseproof feature.Therefore, because CTS divides into groups to be sent to the communication station that is present in up in the scope of the distance identical with dispatching station when from receiving station (CTS dispatching station), so can not fundamentally solve the problem of concealed terminal.In addition, dividing into groups for RTS, equally also is like this.
-problem 2: (influence of NAV is at interval forbidden in transmission)
In addition, according to IEEE802.11, make the terminal that receives the RTS/CTS grouping that is addressed to other-end stop to send and handle (NAV) till accomplishing affairs; Yet the communication that in fact or even not influences the reception in the terminal of having sent CTS also is restricted.Because this operation, the availability of circuit is not enhanced.
Influence when-problem 3:CTS divides into groups not to be returned
When " point of destination of packet " can not receive correctly that RTS divides into groups or when it because certain is former thereby be set as when sending illegal state because CTS divides into groups not to be returned " the transmission source station of packet ", so do not carry out the transmission of packet.Yet, receive near communication station that RTS divides into groups and get into and send illegal state up to the transmission of accomplishing packet and till receiving affairs and no matter whether CTS is returned, this is a trouble.
-problem 4: the imperfect character of transmission rate
Though be necessary to make the transmission rate of packet before sending the RTS grouping, to be determined; But because dispatching station can not obtain the real-time accepting state in the receiving station, therefore with very low with the possibility of the corresponding optimum transmission rate transmission packet of the accepting state of receiving station.
The present invention proposes in view of the above problems, and its purpose is to solve the problem when in communication system such as Wireless LAN system, carrying out access control.
Summary of the invention
The present invention is the communication of in comprising the network of a plurality of communication stations, carrying out; Wherein under carrying out through the situation that detects the access control that communication that the signal that sends from another station divides into groups regularly can be not regularly do not clash with communicating by letter of another station, the field that the visit that the grouping that produces is sent in information that the information in the grouping payload extracted is required and control owing to divide into groups keeps (access reservation) is included in " through handling the header zone that is not easy the to make mistakes physical layer header part like grouping " at least; And can carry out the processing of using this field.
In addition; The present invention is the communication of in comprising the network of a plurality of communication stations, carrying out; Wherein under carrying out through the situation that detects the access control that communication that the signal that sends from another station divides into groups regularly can be not regularly do not clash with communicating by letter of another station; Up to accomplish receiving because the information of the time period till the new grouping that the transmission of associated packets produces is written in the field of the visit reservation that is used for controlling the grouping of sending from communication station, thereby can carry out based on this information processing.
In addition; The present invention is the communication of in comprising the network of a plurality of communication stations, carrying out; Wherein under carrying out through the situation that detects the access control that communication that the signal that sends from another station divides into groups regularly can be not regularly do not clash with communicating by letter of another station; And judge grouping when the destination-address from be included in the header that receive to divide into groups and not be addressed at that time, end process of transmitting, in the visit reserved field in being included in this grouping till represented time.
In addition; The present invention is the communication of in comprising the network of a plurality of communication stations, carrying out; Wherein under carrying out through the situation that detects the access control that communication that the signal that sends from another station divides into groups regularly can be not regularly do not clash with communicating by letter of another station; And when the instruction of returning that in reception is divided into groups, identifies delay confirmation of receipt response signal sends to the transmission source that receives grouping with certain signal afterwards, the confirmation of receipt response signal is included in this signal.
According to the present invention, can enlarge the coverage area that respond packet is confirmed in coverage area of sending the request grouping and the request of sending, therefore a kind of good communication means and communication equipment and computer program can be provided.
In addition, according to the present invention, might prevent the trouble when not returning the request of transmission confirms respond packet.
In addition, according to the present invention, can judge employed transmission rate in the information of transmission according to nearest accepting state, thereby can accurately carry out the selection of transmission rate.
Description of drawings
Fig. 1 is the layout example description figure according to the communication equipment of the embodiment of the invention;
Fig. 2 is the ios dhcp sample configuration IOS DHCP block diagram according to the communication equipment of the embodiment of the invention;
Fig. 3 is the detailed configuration example block diagram according to the communication equipment of the embodiment of the invention;
Fig. 4 is the example description figure according to the frame format of the embodiment of the invention;
Fig. 5 is the example sequential chart of the CSMA/CA (example 1) according to the embodiment of the invention;
Fig. 6 is the example sequential chart of the CSMA/CA (example 2) according to the embodiment of the invention;
Fig. 7 is the example description figure according to the frame field of the embodiment of the invention;
Fig. 8 is the example description figure according to the transmission of the embodiment of the invention and receiving course (example 1);
Fig. 9 is the example description figure according to the transmission of the embodiment of the invention and receiving course (example 2);
Figure 10 is the example description figure according to the transmission of the embodiment of the invention and receiving course (example 3);
Figure 11 is the example sequential chart of traditional access control;
Figure 12 is legacy packets example description figure at interval;
Figure 13 is the example description figure of conventional frame format;
Figure 14 is the example description figure of conventional frame field; And
Figure 15 is the example sequential chart of traditional C MA/CA.
Embodiment
Below will be referring to figs. 1 through 10 explanation embodiments of the invention.
The communication transmission path of supposition is wireless in the present embodiment, and supposition uses single transmission medium in the situation of setting up network between a plurality of equipment (under the situation that link does not separate through frequency channels).Yet, even exist a plurality of frequency channels to be suitable for too as transmission medium.In addition, the communication of supposition in the present embodiment is the communication of storage forwarding type, and information is transmitted to be grouped into the unit.
In addition, each communication station can also carry out the specific communication that is used for direct transmission information under asynchronous mode according to the access process based on CSMA (carrier wave detection multiple access).
In not having the specific autonomous distributed wireless communication system of this type of installing control station; Each communication station through on the channel near other communication stations notice beacon messages make its exist near other communication stations know, and to they informing network structures.Because communication station sends beacon in the beginning of transmit frame circulation, so the transmit frame circulation defines with beacon interval.And; Each communication station is through only carrying out scan operation on this channel in the time period that equals the transmit frame circulation; The beacon signal that discovery is sent near station, and through decoding and know network configuration (perhaps getting into network) being written in information in the beacon.
Fig. 1 illustrates the example according to the layout that is included in the communication equipment in the wireless communication system of the embodiment of the invention.In this wireless communication system, do not install specific control station, and each communication equipment with autonomous dispersing mode work to form ad hoc network.In this accompanying drawing, communication equipment #0 is shown is distributed on the state in the same space to #6.
In addition; In this accompanying drawing; The communication range of each communication equipment shown in broken lines, and not only communication can be carried out with another communication equipment that is present in this scope each other, and also this scope is defined as the scope of being disturbed other communication equipments by the signal that himself sends.In other words, communication equipment #0 be in can with the scope of near communication equipment #1 and #4 executive communication in; Communication equipment #1 be in can with the scope of near communication equipment #0, #2 and #4 executive communication in; Communication equipment #2 be in can with the scope of near communication equipment #1, #3 and #6 executive communication in; Communication equipment #3 be in can with near the scope of communication equipment #2 executive communication in; Communication equipment #4 be in can with the scope of near communication equipment #0, #1 and #5 executive communication in; Communication equipment #5 be in can with near the scope of communication equipment #4 executive communication in; And communication equipment #6 be in can with near the scope of communication equipment #2 executive communication in.
When executive communication between some particular communication devices, there be " concealed terminal ", just, can be heard by the communication equipment of communication counterpart but the communication equipment that can not be heard by communication equipment at opposite side in a side.
Fig. 2 is wireless transmission and the ios dhcp sample configuration IOS DHCP block diagram of receiving equipment of forming the communication station of the system be applied to present embodiment.In this example, antenna 1 is connected to reception processing unit 3 and sends processing unit 4 through antenna shared cell 2, and reception processing unit 3 is connected to Base Band Unit 5 with transmission processing unit 4.For the receiving handling method and the receiving handling method that sends in the processing unit 4 that receive in the processing unit 3, for example can use the various communication meanss that are suitable for relative shorter range communication and are applicable to WLAN.Specifically, can use UWB (ultra broadband) method, OFDM (OFDM) method, CDMA (Code Division Multiple Access) method etc.
Base Band Unit 5 comprises interface 6, MAC (medium access control) unit 7, DLC (data link control) 8 etc., and in each processing unit, carries out each layer processing according to access control method that in this communication system, realizes.
Fig. 3 further is shown specifically the functional structure that is used as according to the Wireless Telecom Equipment of the communication station in the wireless network of the embodiment of the invention.Wireless Telecom Equipment shown in this accompanying drawing can form network, simultaneously through carrying out the intrasystem channel access of same wireless and avoid conflict not installing under the autonomous decentralized communication environment of control station.
As shown in Figure 3, Wireless Telecom Equipment 100 comprises: interface 101, data buffer 102, central control unit 103, beacon generation unit 104, wireless transmission unit 106, timing control unit 107, antenna 109, radio receiving unit 110, beacon analytic unit 112 and information memory cell 113.
Interface 101 and the external equipment that is connected to Wireless Telecom Equipment 100 (for example, personal computer (not shown) etc.) exchange various information sets.
Data buffer 102 is used for the data that interim storage is sent from the equipment that is connected through interface 101, and is used for being stored in the data that receive through wireless propagation path before sending through interface 101 temporarily.
Central control unit 103 is carried out a series of information in the Wireless Telecom Equipment 100 uniformly and is sent and receive and handle and the management of transmission path access control.Conflict when executable operations is controlled beacon collision for example in central control unit 103 is avoided handling.As the processing procedure that conflict is avoided, termination, the beacon to another station that the beacon that can list the station sends the skew of position, its beacon transmission send position change request (beacon sends skew or its termination of position) etc.; And the details of these processing procedures will be described in the back.
Beacon generation unit 104 produces periodically the beacon signal with near Wireless Telecom Equipment exchange.In order to let Wireless Telecom Equipment 100 utilize wireless network, specify its beacon send position, near the beacon receiving position at station etc.These information stores in information memory cell 113, and through writing information in beacon signal come near Wireless Telecom Equipment notify these information.For the structure of beacon signal, the back will be explained.Because Wireless Telecom Equipment 100 sends beacon in the beginning of transmit frame circulation, therefore define by beacon interval by the circulation of the transmit frame in the channel of Wireless Telecom Equipment 100 uses.
Wireless transmission data and beacon signal that 106 pairs of wireless transmission unit are stored in the data buffer 102 are temporarily carried out the predetermined modulation processing.In addition, radio receiving unit 110 is carried out at the fixed time from the information of another Wireless Telecom Equipment transmission and the reception of signal such as beacon signal and is handled.
As wireless transmission and the method for reseptance in wireless transmission unit 106 and the radio receiving unit 110, for example can use the various communication meanss that are suitable for relative shorter range communication and are applicable to WLAN.Specifically, can use UWB (ultra broadband) method, OFDM (OFDM) method, CDMA (Code Division Multiple Access) method etc.
Antenna 109 wireless transmission on pre-specified frequency channel is addressed to the signal of another Wireless Telecom Equipment, perhaps collects the signal that sends from another Wireless Telecom Equipment.In the configuration of Fig. 3, an antenna only is provided, thereby can not executed in parallel sends and receive.
Timing control unit 107 is carried out the timing controlled that is used to send and receive wireless signal.For example, control its beacon of being positioned at transmit frame circulation stem sends regularly, receives regularly, sends and receive regularly with the data of another communication equipment and scan operation circulation etc. from the beacon of another communication equipment.
Beacon analytic unit 112 is analyzed the beacon signal that receives near station, and near the existence of the Wireless Telecom Equipment of analysis etc.For example, the reception information regularly such as the reception of the beacon in adjacent station timing and near relevant beacon is stored in the information memory cell 113 as near facility information.
Information memory cell 113 is stored in the central control unit 103 the implementation order carried out (describing the program that processing procedure etc. is avoided in conflict) like a series of access control operations, near the facility information that from the analysis result that receives beacon, obtains etc.
Next step, Fig. 4 illustrates the example according to the frame format of the grouping of present embodiment.The preposition stem that is added to each grouping of expression grouping existence.Then, after preposition, defined signal field.In signal field; Stored the message part (payload) that the divides into groups required information of decoding, compared top grade comprising the tail of the data length field of the speed field of the transmission rate of expression message part, expression message part length, Parity Check Bits, encoder.To this point, frame format is identical with prior art (example of Figure 14).
In addition, in the present embodiment, " the PLCP header of supposition physical layer header for through handling the header zone be difficult for makeing mistakes ", and as the field of PLCP header, wherein the PLCP header is a physical layer header, exists: power field, expression grouping transmitted power; Duration field, expression are accomplished the transmission of dividing into groups and are received afterwards up to the duration of accomplishing till sending the grouping that will send owing to receive above-mentioned grouping; And classification field, comprise the relevant information that receives response confirmation of whether before the transmission of that grouping, carrying out.
For example; When communication equipment #0 sends data to communication equipment #1; For the CTS that protects the communication equipment #1 that produces owing to the RTS grouping of being sent by communication equipment #0 divides into groups to send, in the duration field that RTS divides into groups, write the time period till accomplishing slave unit #1 transmission CTS.Because other-end was forbidden sending before the transmission of accomplishing CTS, therefore can protect from the CTS of communication equipment #1 and divide into groups to send.Similarly, the duration field of the packet that sends to communication equipment #1 from communication equipment #0, write up to the time period of accomplishing till slave unit #1 sends ACK.Therefore; According to present embodiment; For the temporal information that in the duration field, is provided with, the transmission quality of the grouping of considering to be received before the next-door neighbour confirm the transmission rate of the next one grouping that will send, and the duration value of calculating from determined transmission rate can be set.Thereby, when sending RTS, confirmed data rate according to tradition owing to send the station of RTS with the calculating prolongeding time value, therefore having a problem is can not consider to change owing to the transmission rate that the variation of state later in the transmission path produces; Yet, according to present embodiment, this problem does not take place.
In addition,, be longer than required NAV, therefore improved the availability of medium owing to irrespectively carry out feasible setting of control with the kind of sending divide into groups (RTS, CTS, data, ACK etc.) according to present embodiment.
In addition; Though can confirm to be stored in the duration field up to the time period of accomplishing till sending the grouping of sending owing to the reception associated packets from the transmission time started of associated packets; But the grouping in the transmitting time section is sent and is unconditionally forbidden; Therefore its operation omits its explanation below much at one in prior art.
Originally, had only the required information of the associated packets of reception to be written in the PLCP header; Yet; In the present embodiment, the provisioning information of not only above-mentioned information but also relevant " whether before dividing into groups to send, carry out and receive response confirmation " and relevant " because that grouping of reception and grouping below will sending " below the reservation information of grouping be written in the PLCP header.In addition, also exist the transmitted power of associated packets also to be written into to be used as an information that is used for determining transmitted power the recipient.Remainder keeps identical with prior art.Though explanation has defined the example of all these fields below for the purpose of the simplified illustration, all these fields there is no need all to be defined to obtain validity of the present invention.
Be not addressed at that time when identifying the branch group of received and judging grouping according to the decoded result of PSDU, each communication station carries out and makes the always forbidden processing on the represented time period of the duration field that is sent in the PLCP header.
And; Identifying the branch group of received and judging according to the decoded result of PSDU under the situation that grouping is not addressed to it; And when extracting the information of representing " before the transmission of dividing into groups, carrying out the reception response confirmation " when the classification field from the PLCP header; Each communication station receives operation and stops judging to make when grouping is not addressed to it, and changes normal transmission and accepting state over to.
Special antinoise is the signal section that the good coding of noise characteristic is applied to store the PLCP header, and sends with the for example about 4Mbps that is lower than the minimum-rate that sends message part (payload portions).In addition, when receiving that SNR is low to make that received power is also low, can not find preposition part, and can not identify and divide into groups to be received.Therefore, when identifying grouping and be received, can extract the duration field error-free and irrelevant with the transmission rate of message part.
Fig. 7 is the figure that the frame field of PSDU is shown.Here, the four kinds of required frames of aspect that only explanation are different from prior art describe.
In each frame, define the frame control field of information of the kind, use etc. of storage representation frame jointly.In this field, do not arrange according to the existing duration field of tradition, because according to present embodiment, sending duration field in as the PLCP header of physical layer header.In Frame,, also there be the ACK type field and the ACK SEQ field of expression ACK of expression ARQ method to picture frame except according to the defined field of tradition.In the RTS frame, except according to the defined field of tradition, the data length field of the bit number of the Frame that the ACK type field, expression ACK that also has an expression ARQ method sends after to the ACK SEQ field of picture frame and expression.In the CTS frame,, also there is the speed field of the transmission rate of the Frame that sends after the expression, the ACK type field of representing the ARQ method and expression ACK ACK SEQ field to picture frame except according to the defined field of tradition.In the ACK frame,, also there be the ACKSEQ field of expression ACK to picture frame except according to the defined field of tradition.
When receiving grouping, communication station judges through the destination address field of reference frame whether grouping is addressed to it, and this is similar to the prior art example.
-CSMA process
Fig. 6 is the RTS/CTS procedural example figure according to present embodiment.
In Fig. 6, suppose the state described in the prior art example that is same as Figure 15.Mainly be to describe below, and the explanation that is similar to the process of prior art example is omitted by part to being different from the prior art part.
Confirming medium according to traditional C MA process after special time period (from time T 0 to time T1) is without hindrance, the STA0 of communication station begins to send the RTS that is addressed to the STA2 of communication station in time T 1 and divides into groups.Time period (that is the time period from T2 to T4) up to accomplishing till receiving the CTS that sends owing to reception RTS is written in the duration field of RTS grouping.Here, also some tolerance limits might be provided, make that the time period till whenabouts T5 is written in the duration field as the time span that is written into the time period till time T 4.In addition, the information of representing " before sending grouping, not having the packet switching (specifically, be adjacent to time T 1 and do not receive any grouping from the destination that RTS divides into groups before) with the recipient " is written in the classification field.In addition, the information of the transmitted power of expression RTS grouping is written in the power field.And the information that expression is stored in the bit number in the packet of being sent thereafter by the expection next-door neighbour is written in the data length in the PSDU.
This RTS divides into groups also to be received near the STA2 of communication station that is arranged in the STA0 of communication station.Even the STA2 of communication station fails in PSDU is decoded, also probably correctly the PLCP header portion is decoded, because this part is good aspect noise characteristic.Speed field from the PLCP header and data length field recognition time T2, and through further coming recognition time T4 with reference to the duration field are to realize sending and forbid through NAV is set at the time durations till T4.
The STA1 of communication station that this RTS grouping also is used as the destination receives.The STA1 of communication station decodes to the PLCP header, and can be through attempting in the time period till T4, to be provided with NAV with reference to duration field in the PLCP header etc. with the mode that is similar to the STA2 of communication station; Yet, when also successfully identifying this grouping in PSDU is decoded, STA1 is addressed at that time, do not carry out the setting of NAV.In addition, STA1 identifies existence is addressed to its packet from the STA0 of communication station transmission request, and the time T 3 after the SIFS interval is returned the CTS grouping.The STA1 of communication station is evaluated at the quality of returning the RTS grouping that receives before the CTS grouping, and according to this assessment result, the transmission rate of definite packet of sending later on.Because deterministic process is not the characteristic of present embodiment, therefore will omit its explanation.
After confirming transmission rate; According to the time span of bit number in the packet of representing by the RTS grouping and the grouping of determined transmission rate calculated data, and in the duration field in the PLCP header that is written in the CTS grouping as the time period till the T6 that accomplishes the time of sending the packet of sending owing to reception CTS grouping with the mode that is similar to said process.The situation that also has the time till about T7 that writes in order to have certain tolerance limit.In addition, because owing to the CTS grouping transmission in the transmission source that is addressed to the RTS grouping is carried out in reception RTS grouping, so in classification field, write the information of expression " existence grouping transmission existence before and recipient's packet switching ".
In addition, be written in that represented transmitted power is made as transmitted power in the power field of RTS in dividing into groups, and represented that the value of this transmitted power is written in the power field.If the STA1 of communication station can not send to be written in transmitted power represented in the power field in the RTS grouping; Then in STA1 can carry out the transmit power range of transmission, be provided with divide into groups with RTS in the represented immediate value of transmitted power, and this transmitted power is written in the power field that CTS divides into groups.In addition, determined transmission rate is written in the speed field in the PSDU that CTS divides into groups.Carry out the transmission of the PSDU of CTS grouping itself with the transmission rate of noise characteristic good (being most excellent under many circumstances), so that can reduce the possibility that to decode to the CTS grouping as much as possible.
On the other hand; When the STA1 of communication station fails in when PSDU decoded; Even its success is decoded in the PLCP header that RTS is divided into groups, the STA1 of communication station also becomes the transmission illegal state through in the time period till T4 represented the duration field that obtains from the PLCP header etc. NAV being set.In this case, divide into groups owing to do not return CTS before the T4, so the STA0 of communication station attempts to resend the RTS grouping according to stochastic backoff process from the STA1 of communication station in expeced time.At this moment, the STA2 of communication station also removes NAV in time T 4, thereby but get into normal transmit status, and can farthest be minimized owing to CTS divides into groups not to be returned the destruction that causes.
When the STA1 of communication station is successful when the PSDU that RTS is divided into groups decodes, return CTS in time T 4 according to expection according to said process and divide into groups.Divide into groups owing to transmit CTS, therefore probably can carry out transmission and the reception of PSDU error-free with the good transmission rate of noise characteristic.
This CTS divides into groups also to be received by near the STA3 of communication station that is positioned at the STA1 of communication station.Duration field in the PLCP that the STA3 of communication station divides into groups to CTS etc. is decoded, and confirms that the RA address among the PSDU is not addressed at that time, and the STA3 of communication station is provided with NAV on represented time period in duration field etc., sends stopping.As a result, the STA3 of communication station becomes till the T6 that sends illegal state represented time in as the duration field.
This CTS divides into groups also to be received by the STA0 of communication station as the destination.Through PSDU is decoded, the STA0 of communication station identifies the STA1 of communication station and prepares reception and expect to receive with transmission rate represented in the speed field.The STA0 of communication station produces packet with indicated transmission rate in being same as above-mentioned process, and will be written in the duration field of PLCP header up to accomplishing the time period that receives till the ACK that sends owing to the reception packet divides into groups.And, because carry out the packet transmission in the transmission source that is addressed to the CTS grouping, so in classification field, write the information of expression " existence and recipient's packet switching before sending associated packets " owing to receiving the CTS grouping.
In addition, be written in that represented transmitted power is made as transmitted power in the power field of CTS in dividing into groups, and in the power field, write the value of this transmitted power of expression.If the STA0 of communication station can not send to be written in transmitted power represented in the power field in the CTS grouping; Then in the STA0 of communication station can carry out the transmit power range of transmission, be provided with divide into groups with CTS in the represented immediate value of transmitted power, and in the power field of the packet that is sent out, write this transmitted power.The packet that in said process, is produced begins after the SIFS interval, to be sent out with the time T 5 of dividing into groups from CTS.
In addition, when the transmitted power of the previous RTS grouping that has been sent out is different from transmitted power represented in the CTS grouping, also there is the situation that the transmitted power when sending the RTS grouping is set.
Packet is received by near the STA2 of communication station that is positioned at the STA0 of communication station; And the PLCP header information through during data are divided into groups is decoded; The STA2 of communication station understands the transmission of till time T 6, carrying out packet, and expection is under an embargo till time T 8 after this transmission; And the STA2 of communication station is provided with NAV from time T 6 to time T8 so that transmission is under an embargo.Even the PSDU of packet can not also be carried out this process by correct decoding.
Naturally; Packet is also received by the STA1 of communication station as the destination; And when accomplishing packet transmissions and the STA1 of communication station in time T 6 and can decode to this error-free; Return ACK in the time T 7 of SIFS after at interval, and the STA0 of communication station receives this, thereby accomplish the transmission and the reception affairs of a grouping in time T 8.Divide into groups though the STA1 of communication station basis identical process when producing CTS and divide into groups produces ACK, the STA1 of communication station through storage 0 value in the duration field in the PLCP header that divides into groups at ACK wait near station notice " accomplish ACK do not exist after dividing into groups to send make the forbidden time zone of transmission ".
The STA3 of communication station removes NAV in time T 6, and the STA2 of communication station is at time T 8 removing NAV, to turn back to normal transmission and accepting state.
Fig. 5 is another exemplary plot according to the RTS/CTS process of the embodiment of the invention.
Be similar to IEEE802.11, to return Fig. 6 situation that ACK divides into groups after the packet be example to be adjacent to; Yet, also have the situation that the ACK grouping is returned in packet afterwards that is not adjacent to.The example of this situation is described in Fig. 5.
Expection makes and is sent in that forbidden time span is that unit is written in the duration field of the grouping of being sent in the example of Fig. 5 with [μ second] after the transmission of accomplishing associated packets.Yet; The duration field is not always to comprise that with [μ second] be the field that unit writes length information; And can indicate the communication station that is different from the destination on the expected time section, to be in the information or the information sets of sending illegal state as long as the duration field comprises, just can realize its purpose.
In classification field, when sending associated packets under the situation that is not having previous notice when (for example, RTS divides into groups); Storage 1 value; And, store 0 and be worth when transmission grouping under the situation of previous notice being arranged when (for example, dividing into groups to divide into groups) as the CTS that sends through receiving RTS.
Following table has been summarized the relation between the value of value and classification field of duration field.
The duration field 1 or bigger value 1 or bigger value 0 0
Classification field 1 0 1 0
Treatment state The grouping reception period and in the duration represented time period forbid the time period for sending. Though it is possible sending at the grouping reception period, the time period represented in the duration is for sending disable period.Perhaps, the grouping reception period and in the duration represented time period forbid the time period for sending. Forbid the time period for sending up to accomplishing the time that receives till dividing into groups. Be in 0 identifying duration and classification field, send the possibility that becomes.
[0111]In the example of Fig. 5; Till time T 5, take and identical process shown in Figure 6; And when the STA0 of communication station when time T 5 is sent packets; Through middle storage 0 values such as the duration fields in the PLCP header, " after completion transmission ACK divides into groups, do not make and send the forbidden time period " near station notice.
This packet is received by near the STA2 of communication station that is positioned at the STA0 of communication station; And the information through in the PLCP header that data are divided into groups is decoded; The STA2 of communication station identified before the transmission of that grouping and has carried out packet switching with the recipient; The transmission of carrying out that packet and does not exist after this to make and sends the forbidden time period till time T 6; In addition, the STA2 of communication station is through knowing that with reference to the destination address field of PSDU grouping is not addressed to it.Then; (knowing that grouping is not addressed to it; In the packet switching of sending that divide into groups existence before and recipient; And after the transmission of accomplishing that grouping, do not exist to make send after the forbidden time period), the STA2 of communication station operates knowing to finish to receive when grouping is not addressed to it, and turns back to normal transmission and accepting state.When the STA2 of communication station handles the data that should be sent out, activate the stochastic backoff process of CSMA, be used to obtain the process of transmission route thereby activate.
Other processes are said identical with Fig. 6.Yet; When packet is also received by the STA1 of communication station as the destination; And when the transmission of having accomplished packet in time T 6 and the STA1 of communication station can decode to this packet error-free, carry out the transmission that ACK divides into groups with another chance.According to process shown in Figure 5, because the STA2 of communication station can avoid in conventional method shown in Figure 15 transmission till time T 8 to forbid the state under the time period, so circuit efficient will be enhanced.
-ACK mutation
Use Fig. 8 to 10 that the ARQ process that the situation of ACK grouping is returned in packet afterwards of sending that is not adjacent to as shown in Figure 5 is described.In this case; Exist at least two mutation as the method that is used to return ACK; Wherein define ACK immediately as shown in Figure 5 and postponed ACK; In ACK immediately, be adjacent to and return ACK after receiving packet error-free, and in postponing ACK, when receiving packet error-free, the predetermined amount of time till sending ACK is being carried out returning ACK after the timing.Following process adopts by postponing ACK.
1. when receiving packet error-free, activate, and when timer finishes (expiration), attempt to send ACK and divide into groups up to the timer that sends till ACK divides into groups.
2. when before above-mentioned timer finishes, sending when being addressed to certain of purpose communication station that Ying Xiangqi returns ACK and dividing into groups, also in these data, write ACK information, and the above-mentioned timer that resets.
Also can be with following process as another example that postpones ACK.
1. when receiving packet error-free, record receives the situation of dividing into groups error-free; Yet ACK is not sent out.
2. divide into groups to make when being sent out when being addressed to certain of purpose communication station that Ying Xiangqi sends ACK, also write ACK information in the data that will send.
3. when at the fixed time in the section when not returning ACK, sending the request (request-to-resend) that resends for the data of being sent.
In this case, be different from above-mentioned example, do not comprise the timer that is used to return ACK.The control that is used in section at the fixed time, sending when not returning ACK the request that resends is the process that generally resends.
In ACK, exist under the situation of a plurality of mutation; As shown in Figure 7 the ACK type field of definition expression ACK echo plex mode in the control frame etc. of the data that will send; And write expression in transmit leg this field in RTS frame and Frame and return the solicited message of the mode of ACK, and write the affirmation information of expression ACK echo plex mode in this field in the CST frame from the recipient.In addition, because therefore the possibility that exists each frame to be shared by ACK has defined ACK SEQ field.The use of ACK SEQ field is described below.
For example, suppose that the STA0 of communication station sends the situation of the link layer packet with SEQ numbering 023 to the STA1 of communication station.At this moment, numbering 023 is written in the SEQ field of packet.For example, when returning the received notice of this packet, numbering 023 is written in the ACK SEQ field.Since can be in any frame of RTS/CTS/ data/ACK the return data received notice of dividing into groups, therefore in all frames shown in Figure 7, defined ACK SEQ field.Here, for the ease of simplified illustration, an ACK SEQ field has only been described; Yet, in fact in each frame, can have a plurality of ACK SEQ fields.
Example shows among-Fig. 8
Fig. 8 is transmission and first exemplary plot of receiving course in the wireless communication system of present embodiment.Here, be example with the situation of sending two data groupings that are addressed to the STA1 of communication station from the STA0 of communication station.
The process of transmitting that the STA0 of communication station divides into groups at time T 0 activation data according to the CSMA process is to begin to keep out of the way timing, so that obtain transmission route.Owing to keep out of the way timing in time T 1 completion, and confirm that medium is without hindrance in this time period, therefore send RTS and divide into groups.At this moment, the request that in the ACK type field of RTS grouping, writes adopts delay ACK to return the information of ACK, and in ACK SEQ field, writes the expression grouping not by the information of ACK information sharing.
The STA1 of communication station that receives above-mentioned information returns CTS in time T 2 and divides into groups.At this moment, in the ACK type field that CTS divides into groups, write and adopt delay ACK to return the affirmation information of ACK as indicated, and in ACK SEQ field, write the expression grouping not by the information of ACK information sharing.
The STA0 of communication station that receives above-mentioned information sends packet in time T 3.At this moment; The request that in the ACK of packet type field, writes is once more adopted and is postponed the information that ACK (postponing Ack) returns ACK; In ACK SEQ field, write expression and divide into groups, and in the SEQ field, write the serial number (for example, 023) of grouping not by the information of ACK information sharing.
The STA1 of communication station that receives above-mentioned information activates the timer that is used to return ACK in time T 4.In addition, before timer finished, the time T 5 of the STA0 of communication station after the delay that the random time section takes place sent the RTS grouping, so that send the packet that is addressed to the STA1 of communication station once more.At this moment, the request that in the ACK type field that RTS divides into groups, writes adopts specifically immediately that ACK returns the information of ACK, and in ACK SEQ field, writes expression and divide into groups not by the information of ACK information sharing.
The STA1 of communication station that receives above-mentioned information returns CTS in time T 6 and divides into groups.At this moment, in the ACK type field that CTS divides into groups, write and confirm to adopt ACK immediately to return the information of ACK.In addition; Because the STA1 of communication station preserves the ACK that is addressed to the STA0 of communication station that is not sent out as yet; Therefore make the ACK information sharing ACK SEQ field of the confirmation of receipt response of dividing into groups, and in ACK SEQ field, write serial number 023 as the Frame of ACK object as previous reception with serial number 023.
The STA0 of communication station that receives above-mentioned information sends next packet in time T 7, confirms to receive error-free previous data frame simultaneously.At this moment; The request of in the ACK of packet type field, writing once more adopts ACK (Ack immediately) immediately to return the information of ACK; In ACK SEQ field, write expression and divide into groups, and in the SEQ field, write the serial number (for example, 024) of grouping not by the information of ACK information sharing.
To send ACK immediately owing to the STA1 of communication station that receives above-mentioned information identifies expection, therefore return ACK immediately in time T 8 specifically and divide into groups.In the ACK SEQ field that ACK divides into groups, write the serial number 024 of previous reception.
Example shows among-Fig. 9
Fig. 9 is transmission and second exemplary plot of receiving course in the wireless communication system of present embodiment.Equally in this example, be example with the situation of sending two data groupings that are addressed to the STA1 of communication station from the STA0 of communication station.
In first example shown in Figure 8, be illustrated in indication lag ACK from first packet that the STA0 of communication station sends and in second packet, indicate the situation of ACK immediately from it.In second example shown in Figure 9, be illustrated in two data divide into groups in situation of indication lag ACK all.Because the process till time T 4 is same as first example of Fig. 8, therefore omit its explanation.
Be similar to above-mentioned first example, the STA1 of communication station activates the timer that is used to return ACK in time T 4.
Before this timer finished, the time T 5 of the STA0 of communication station after the delay that the random time section takes place sent the RTS grouping, so that send the packet that is addressed to the STA1 of communication station once more.At this moment, the request that in the ACK type field that RTS divides into groups, writes adopts delay ACK to return the information of ACK once more, and in ACK SEQ field, writes the expression grouping not by the information of ACK information sharing.
The STA1 of communication station that receives above-mentioned information returns CTS in time T 6 and divides into groups.At this moment, in the ACK type field that CTS divides into groups, writing affirmation adopts delay ACK to return the information of ACK as indicated.In addition; Because the STA1 of communication station preserves the ACK that is addressed to the STA0 of communication station that is not sent out as yet; Therefore make the ACK information sharing ACK SEQ field of the confirmation of receipt response of dividing into groups, and in ACK SEQ field, write serial number 023 as the Frame of ACK object as previous reception with serial number 023.
The STA0 of communication station that receives above-mentioned information sends next packet in time T 7, confirms to receive error-free previous data frame simultaneously.At this moment, the request that in the ACK of packet type field, writes is once more adopted and is postponed the information that ACK returns ACK, in ACK SEQ field, writes expression and divides into groups not by the information of ACK information sharing, and in the SEQ field, write the serial number (for example, 024) of grouping.
The STA1 of communication station that receives above-mentioned information activates the timer that is used to return ACK in confirmation after taking out error-free.Specifically, do not send owing in the time period till timer finishes, be addressed to the grouping of the STA0 of communication station as yet, so the STA1 of communication station activates the process of transmitting of the ACK frame that is addressed to the STA0 of communication station.When timer finished, the time T 9 after the delay that the random time section takes place was sent the ACK frame, so that send the ACK frame.At this moment, in ACK SEQ field, write the numbering 024 of the serial number of the previous receiving data frames of conduct.
Receive the response signal that the STA0 of communication station of above-mentioned information sends that ACK frame immediately in time T 10, identifying serial number through the ACK SEQ field of extracting the ACK frame simultaneously is that 024 packet is by decoding error-free.Response signal is asked to only have and the similar field of traditional ACK frame.
In above-mentioned example; Though the situation example of the timer through being provided for returning ACK with reference to the station that relates to the transmission that postpones ACK and reception and receive data error-free describes, even when not comprising the timer that is used to return ACK, also take sequence much at one.
In this case, time T 9 and this situation takes place thereafter and above-mentioned Fig. 9 between difference.
Though the STA1 of communication station preserves the ACK information that is not returned as yet, this is not sent out as yet.Point at this moment, the STA0 of communication station do not return according to Duan Shangshang at the fixed time and judge serial number 024 at the ACK of time T 7 previous groupings with serial number 024 of sending and possibly not be received as yet; And send in time T 9 and to be used for asking the RTS that resends divide into groups (accompanying drawing is not shown).The time T 10 of the STA1 of communication station after writing the received ACK information of expression grouping that receives above-mentioned information returned CTS grouping (also existing replaced C TS to divide into groups to return the situation that ACK divides into groups).At this moment, because the STA1 of communication station does not ask to resend, therefore storage 0 is worth in the duration field that CTS (ACK) divides into groups.The STA0 of communication station that receives this CTS grouping identifies the grouping with serial number 024 and is received by no any problem ground.
Though the field of the communication station in expression transmission source is not present in above-mentioned example in the ACK frame, also exist the field of the communication station in expression transmission source to be present in the situation in the ACK frame.
Example shows among-Figure 10
Figure 10 is transmission and the 3rd exemplary plot of receiving course in the wireless communication system of present embodiment.Equally in this example, be example with the situation of sending two data groupings that are addressed to the STA1 of communication station from the STA0 of communication station.
In Fig. 8 and example shown in Figure 9, the STA0 of communication station followed stochastic backoff process before sending second packet example is shown.In the 3rd example shown in Figure 10, be shown as an example in two data and all indicate immediately ACK in dividing into groups and allow dispatching station to send the situation that continuous data is divided into groups.
The process of transmitting that the STA0 of communication station divides into groups at time T 0 activation data according to the CSMA process is to begin to keep out of the way timing, so that obtain transmission route.In time T 1, keep out of the way timing owing to accomplish, and confirm that medium is without hindrance in this time period, therefore send RTS and divide into groups.At this moment, the request that in the ACK type field that RTS divides into groups, writes adopts immediately that ACK returns the information of ACK, and in ACK SEQ field, writes expression and divide into groups not by the information of ACK information sharing.
The STA1 of communication station that receives above-mentioned information returns CTS in time T 2 and divides into groups.At this moment, in the ACK type field that CTS divides into groups, write affirmation and adopt as indicated immediately that ACK returns the information of ACK, and in ACK SEQ field, write expression and divide into groups not by the information of ACK information sharing.
The STA0 of communication station that receives above-mentioned information sends packet in time T 3.At this moment, the request of in the ACK of packet type field, writing once more adopts ACK immediately to return the information of ACK, in ACK SEQ field, writes expression and divides into groups not by the information of ACK information sharing, and in the SEQ field, write the serial number (for example, 023) of grouping.In addition, notification data divides into groups also as the RTS message of next packet in classification field etc.
The STA1 of communication station that receives above-mentioned information returns ACK immediately in time T 4.In the ACK type field that ACK divides into groups, write the serial number 023 of previous reception.In addition, notice ACK divides into groups also as the CTS message of next packet in classification field etc.
The STA0 of communication station that receives above-mentioned information sends next packet in time T 5, confirms to receive error-free previous data frame simultaneously.At this moment, the request of in the ACK of packet type field, writing once more adopts ACK immediately to return the information of ACK, in ACK SEQ field, writes expression and divides into groups not by the information of ACK information sharing, and in the SEQ field, write the serial number (for example, 024) of grouping.
To send ACK immediately owing to the STA1 of communication station that receives above-mentioned information identifies expection, therefore return ACK immediately in time T 6 specifically and divide into groups.In the ACK SEQ field that ACK divides into groups, write the serial number 024 of previous reception.
In addition, can consider to send CTS with antimierophonic transmission rate.Owing in the PLCP header, do not write duration field etc., therefore possibly there is the situation that in the telecommunication station, to extract duration field etc. error-free according to the transmission rate of information unit.Yet, use among the CSMA/CA of RTS/CTS process together, be necessary also CTS to be sent to the communication station that might become interference source.
Therefore, divide into groups, send and irrelevant, then might reduce the interference of packet reception period, send and receive thereby can carry out efficiently with the transmission rate of packet etc. etc. if carry out with the most antimierophonic transmission rate for CTS.
Should be noted that; Though the example of the communication equipment that in the above-described embodiments special execution is sent and received is illustrated; But also possiblely be; For example on carrying out the PC device of various data processing, install after the plate that is used to carry out the communication process that transmitting element or receiving element with present embodiment be equal to, the card etc., install software is so that the arithmetic processing device of computer equipment side is carried out the processing in the Base Band Unit.
Reference number is described
The 1-antenna
2-antenna shared cell
3-receives processing unit
4-sends processing unit
The 5-Base Band Unit
The 6-interface
7-MAC (medium access control) unit
8-DLC (data link control) unit
The 100-Wireless Telecom Equipment
The 101-interface
The 102-data buffer
The 103-central control unit
104-beacon generation unit
106-wireless transmission unit
The 107-timing control unit
The 109-antenna
The 110-radio receiving unit
112-beacon analytic unit
The 113-information memory cell

Claims (6)

1. communication means; Be used in comprising the network of a plurality of communication equipments, carrying out access control through detecting from the signal of another equipment transmission; Make the communication of dividing into groups regularly or not clash with communicating by letter of another equipment, this method may further comprise the steps:
It is that the RTS grouping sends to the second communication equipment in the network that first communication equipment from network will ask to send grouping; First communication equipment receives with the request transmission that this request transmission is divided into groups relevant from second communication equipment confirms that respond packet is that CTS divides into groups; Send to confirm respond packet and packet is sent to second communication equipment in response to the request of receiving, and to receive the grouping that relates to the confirmation of receipt response relevant with this packet from second communication equipment be the ACK grouping;
Wherein,, this request transmission writes between the first phase in dividing into groups; Wherein indicate between the first phase from the very first time section of the reception that sends to completion CTS grouping of accomplishing the RTS grouping, and in packet, write the second phase, wherein the second phase indicated from second time period of the reception that sends to completion ACK grouping of accomplishing packet; And
Wherein, in very first time section with during second time period, forbid that the third communication equipment in the network is carried out the transmission processing.
2. communication means according to claim 1, wherein
Said second communication equipment: measure the request that is received and send the quality of dividing into groups; Transmission rate according to the grouping of quality of reception specified data; According to determined transmission rate with in the bit number information of asking to send the data of being notified in the grouping, the time span that calculated data divides into groups;
Write said definite transmission rate in the speed specific field in CTS divides into groups; And
In CTS divides into groups, be used for controlling and visit the time span that the field that keeps writes the packet of being calculated.
3. communication means according to claim 2, wherein
First communication equipment sends packet according to speed that send to confirm appointment in the respond packet in described request with being used for controlling the time span that field that said visit keeps writes.
4. a communication equipment is used for carrying out access control through detection from the signal that another communication equipment in the network sends, and makes communication regularly or not clash with communicating by letter of another communication equipment, and it comprises:
Send and receiving element; Being configured to ask send grouping is that the RTS grouping sends to the second communication equipment in the network; Receiving the request transmission affirmation respond packet of dividing into groups relevant with this request transmission from second communication equipment is that CTS divides into groups; Send to confirm respond packet and packet is sent to second communication equipment in response to the request of receiving, and to receive the grouping that relates to the confirmation of receipt response relevant with this packet from second communication equipment be the ACK grouping; And
Control unit; Be configured in this request transmission is divided into groups, write between the first phase; Wherein indicate between the first phase from the very first time section of the reception that sends to completion CTS grouping of accomplishing the RTS grouping, and in packet, write the second phase, wherein the second phase indicated from second time period of the reception that sends to completion ACK grouping of accomplishing packet; And
Wherein, forbid that the third communication equipment in the network is carried out the transmission processing during the very first time section and during second time period.
5. communication equipment according to claim 4, wherein
Said control unit: make that measuring the described request that in said transmission and receiving element, is received sends the quality of reception of dividing into groups; Transmission rate according to measured quality of reception specified data grouping; According to determined transmission rate with in the bit number information of asking to send the data of being notified in the grouping, the time span that calculated data divides into groups;
Write said definite transmission rate in the speed specific field in CTS divides into groups; And
Being used in CTS divides into groups controlled and visits the time span that the field that keeps writes said packet of calculating.
6. communication equipment according to claim 5, wherein
Said control unit sends the speed of confirming appointment in the respond packet and is used for controlling the time span transmission packet that field that visit keeps writes said according to the described request that in said transmission and receiving element, is received.
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US8619806B2 (en) 2013-12-31
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US7715426B2 (en) 2010-05-11
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US8249093B2 (en) 2012-08-21
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